iPods and mobile phones could be fitted with antitheft devices that detect ‘acoustic fingerprints’ so they only work when they are being used by the registered owner

Researchers have discovered that they can identify individuals from the faint sounds made deep inside the human ear and are now developing security devices using the technology.

The breakthrough could mean that rather than struggling to remember the plethora of passwords and codes used to protect everything from bank accounts to computer logins, consumers would be able to confirm their identity simply by lifting a phone to their ear or putting on a set of headphones.

iPods and mobile phones could be fitted with antitheft devices that detect “acoustic fingerprints” so they only work when they are being used by the registered owner.

“The sounds produced are not audible to the human ear and people are unaware they are being produced in their own ears,” said Dr Stephen Beeby, a reader in engineering at Southampton University who is leading the research.

“With a sensitive enough microphone, these sounds can be captured with a standard computer sound card and the signal can be analysed. We found that they were different from person to person, which gives us a really nice biometric tool.”

The technology uses extremely faint sounds that are produced inside the human ear called otoacoustic emissions.

They are produced by hair cells in the cochlea, which are responsible for detecting sound waves and turning sound into the electrical message that is received by the brain.

It is thought hair cells vibrate to help amplify the signal they receive through the ear. In doing so, they also produce their own sound. Too faint to be detected by the human ear, the noise can be picked up by sensitive microphones.

Otoacoustic emissions are already used by doctors as a way of testing the hearing of babies. A series of quiet clicks are used to stimulate the hair cells and in healthy children they respond with their own sound.

The researchers found that when they compared the sounds produced by hair cells in different individuals they were able to distinguish them.

It is thought that each person’s hair cells produce a slightly different noise, but as the sound travels through the bones in the ear, the ear drum and along the ear canal, which are subtly different in each person, the noise is changed further to make it unique.

Dr Beeby said: “Otoacoustic emissions have been used by the medical profession for many years and anecdotally clinicians could tell different people’s traces apart.

“When we looked at it we found that otoacoustic emissions really are unique from person to person. As the sound produced will change with the signal put in, we can use standardised signals that produce traces that can be compared.

“It could be surreptitious as you don’t necessarily know when your emissions are being captured.

“When you phone your bank, they could send out a series of clicks through your headset or phone and analyse the response to confirm whether you are who you say you are.”

Biometric identification has become an increasingly popular way of confirming a person’s identity because it relies upon unique physical traits that are difficult to steal and replicate.

The Home Office is pushing to include biometric information using facial recognition software on passports. Travellers have the option to use iris scanning at some UK airports while asylum seekers are required to register their fingerprints.

Banks are also starting to look to biometrics as fears increase over internet viruses that can steal customers’ passwords and pin codes.

The researchers are beginning discussions with security and communications firms to develop acoustic security devices.

“Used in combination with other biometrics, otoacoustic emissions could provide a powerful way of confirming people’s identity,” explained Dr John Chad, a neuroscientist at Southampton University who is also taking part in the research.

“We have got it working in the lab, but we are still a long way from getting this to work reliably in the real world.

“Initially it may be easier to develop a theft deterrent for devices like MP3 players and mobile phones we could use it to discriminate between individuals.

“People who use these devices all use earphones or hold them to their ears, so their otoacoustic emission could be compared to that from the registered user and if it doesn’t match then the device is disabled.”

Biometrics experts at the Home Office have already been to the university look at the new technology and are monitoring its development in the hope that it can be used by the Government.

Marek Rejman-Green, head of the Biometrics Centre of Expertise at the Home Office Scientific Development Branch, said: “The point about biometrics is that one size does not fit all, so it is important that the research in areas that are promising like this is supported by research funding.

“We follow this kind of work so when it does become clearer what the performance is, the government is able to take advantage of it. It will need to be challenged against existing biometric technologies to test its benefit and accuracy.”